Coffee compound may boost solar cells performance

Caffeine -- a chemical found in tea and coffee -- can help make traditional silicon solar cells more efficient at converting light to electricity, a study has found.

The research, published 25 in the journal Joule, may enable this cost-effective renewable energy technology to compete on the market with silicon solar cells.

The idea began as a joke over morning coffee, according to the researchers, who wondered whether coffee could help perovskite solar cells perform better the same way the beverage boosts energy in humans.

The idea led the team at University of California, Los Angeles (UCLA) in the US recall that the caffeine in coffee is an alkaloid compound containing molecular structures that could interact with the precursors of perovskite materials -- compounds with a particular crystal structure that form the light-harvesting layer in a class of solar cells.

Previous attempts to improve the thermal stability of these solar cells have included enhancing the perovskite layer by introducing compounds such as dimethyl sulfoxide, but researchers have struggled to boost the cells' efficiency and long-term stability. No one had tried caffeine.

Realising they might be onto something, the team set aside their coffee and began investigating further.

They added caffeine to the perovskite layer of forty solar cells and used infrared spectroscopy (which uses infrared radiation to identify chemical compounds) to determine that the caffeine had successfully bonded with the material.

Conducting further infrared spectroscopy tests, they observed that the carbonyl groups (a carbon atom double bonded to an oxygen) in caffeine interacted with lead ions in the layer to create a "molecular lock."